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Radios

Main articles: Radiation astronomy/Radios and Radio astronomy

This image has the radio image of Greg Taylor, NRAO, overlain on the X-ray image from Chandra. The radio source Hydra A originates in a galaxy near the center of the cluster. Optical observations show a few hundred galaxies in the cluster. Credit: NASA/CXC/SAO; Radio: NRAO.

Radio waves are a type of electromagnetic radiation with wavelengths in the electromagnetic spectrum longer than infrared light. Radio waves have frequencies from 300 Gigahertz (GHz) to as low as 3 kilohertz (kHz), and corresponding wavelengths from 1 millimeter to 100 kilometers.

Several satellites have served as observatories for radio waves and specifically for microwaves. The Radio Astronomy Explorer (RAE) 1 is launched into orbit on July 4, 1968, around Earth, while the Explorer 49 (RAE 2) was launched on June 10, 1973, around the Moon.

The COBE was launched into Earth orbit on November 18, 1989. The WMAP was launched on June 30, 2001, into orbit at the Lissajous orbit Lagrange 2 location. Both satellites have aboard detectors designed to perform microwave astronomy, as these are limited to only the microwave band.